Hybrid electrically- and mechanically-stimulating cochlear implant

ABSTRACT

Wires and coils within an electrode assembly electromagnetically interact and cause mechanical motion of the assembly. This mechanical motion can be used to supplement or replace the electrical stimulation provided by a standard cochlear implant and provides targeted acoustic stimulation to the cochlea.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.15/416,765, titled HYBRID ELECTRICALLY- AND MECHANICALLY-STIMULATINGCOCHLEAR IMPLANT, filed on Jan. 26, 2017, that claims priority to U.S.Provisional Application No. 62/289,003, titled HYBRID ELECTRICALLY- ANDMECHANICALLY-STIMULATING COCHLEAR IMPLANT, filed on Jan. 29, 2016, thedisclosure of which are hereby incorporated by reference in theirentirety.

BACKGROUND

Hearing loss, which can be due to many different causes, is generally oftwo types: conductive and sensorineural. In many people who areprofoundly deaf, the reason for their deafness is sensorineural hearingloss. Those suffering from some forms of sensorineural hearing loss areunable to derive suitable benefit from auditory prostheses that generatemechanical motion of the cochlea fluid. Such individuals can benefitfrom implantable auditory prostheses that stimulate nerve cells of therecipient's auditory system in other ways (e.g., electrical, optical,and the like). Cochlear implants are often proposed when thesensorineural hearing loss is due to the absence or destruction of thecochlea hair cells, which transduce acoustic signals into nerveimpulses. Auditory brainstem implants might also be proposed when arecipient experiences sensorineural hearing loss if the auditory nerve,which sends signals from the cochlear to the brain, is severed or notfunctional.

Conductive hearing loss occurs when the normal mechanical pathways thatprovide sound to hair cells in the cochlea are impeded, for example, bydamage to the ossicular chain or the ear canal. Individuals sufferingfrom conductive hearing loss can retain some form of residual hearingbecause some or all of the hair cells in the cochlea function normally.

Individuals suffering from conductive hearing loss often receive aconventional hearing aid. Such hearing aids rely on principles of airconduction to transmit acoustic signals to the cochlea. In particular, ahearing aid typically uses an arrangement positioned in the recipient'sear canal or on the outer ear to amplify a sound received by the outerear of the recipient. This amplified sound reaches the cochlea causingmotion of the perilymph and stimulation of the auditory nerve.

In contrast to conventional hearing aids, which rely primarily on theprinciples of air conduction, certain types of hearing prosthesescommonly referred to as bone conduction devices, convert a receivedsound into vibrations. The vibrations are transferred through the skullto the cochlea causing motion of the perilymph and stimulation of theauditory nerve, which results in the perception of the received sound.Bone conduction devices are suitable to treat a variety of types ofhearing loss and can be suitable for individuals who cannot derivesufficient benefit from conventional hearing aids.

SUMMARY

The cochlea is a spiral shaped structure and is tonotopically arrangedsuch that lower frequencies are picked up by nerves at the apex of thecochlear and higher frequencies stimulate nerves at the base. In acochlear implant, a standard intra-cochlear stimulating assembly thereofincludes multiple wires that conduct electrical signals to each of theelectrode pads on the assembly. These pads provide electricalstimulation to the cochlea nerves and therefore provide hearing. Thetechnologies described herein use wires and coils within a stimulatingassembly to electromagnetically interact and cause mechanical motion ofthe assembly. This mechanical motion can be used to supplement theelectrical stimulation and provide targeted acoustic stimulation to thecochlea. Low frequency acoustic stimulation can be achieved by disposingthe coils proximate the tip of the assembly.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The same number represents the same element or same type of element inall drawings.

FIG. 1 is a partial view of a behind-the-ear auditory prosthesis worn ona recipient.

FIG. 2 is a side view of an example of an implantable portion of anauditory prosthesis.

FIG. 3 is a schematic diagram of a hybrid electrically- andmechanically-stimulating cochlear implant.

FIGS. 4-7 are partial schematic views of intra-cochlear regions ofhybrid stimulating assemblies.

FIG. 8 depicts a method of providing stimuli with a hybrid stimulationassembly.

DETAILED DESCRIPTION

Referring to FIG. 1, cochlear implant system 100 includes an implantablecomponent 144 typically having an internal receiver/transceiver unit132, a stimulator unit 120, and an elongate lead 118. The internalreceiver/transceiver unit 132 permits the cochlear implant system 110 toreceive and/or transmit signals to an external device. The externaldevice may be a button sound processor worn on the head that includes areceiver/transceiver coil and sound processing components, areceiver/transceiver coil in communication with a BTE device thatincludes the sound processing components and microphone, a charger for atotally implantable device (such as a totally implantable cochlearimplant or middle ear implant), a clinical diagnostic system or anyother component capable of exchanging power and/or data signals with theimplantable component 144.

The implantable component 144 includes an internal coil 136, andpreferably, a magnet (not shown) fixed relative to the internal coil136. The magnets facilitate the operational alignment of the externaland internal coils, enabling internal coil 136 to receive power andstimulation data from external coil 130. The external coil 130 iscontained within an external portion 150.

Internal receiver unit 132 and stimulator unit 120 are hermeticallysealed within a biocompatible housing, sometimes collectively referredto as a stimulator/receiver unit. The stimulator/receiver unit receivespower and/or data signals from external device and produces stimulationsignals that are transmitted via an elongate lead 118 to the cochlea140. Elongate lead 118 has a proximal end connected to stimulator unit120, and a distal end implanted in cochlea 140. Elongate lead 118extends from stimulator unit 120 to cochlea 140 through mastoid bone119.

In certain examples, external coil 130 transmits electrical signals(e.g., power and stimulation data) to internal coil 136 via a radiofrequency (RF) link, as noted above. Internal coil 136 is typically awire antenna coil comprised of multiple turns of electrically insulatedsingle-strand or multi-strand platinum or gold wire. The electricalinsulation of internal coil 136 is provided by a flexible siliconemolding. Various types of energy transfer, such as infrared (IR),electromagnetic, capacitive and inductive transfer, can be used totransfer the power and/or data from external device to cochlear implant.

FIG. 2 is a simplified side view of an internal component 244 having astimulator/receiver unit 202 which receives encoded signals from anexternal component of the cochlear implant system. Internal component244 terminates in a stimulating assembly 218 that comprises anextra-cochlear region 210 and an intra-cochlear region 212.Intra-cochlear region 212 is configured to be implanted in therecipient's cochlea and has disposed thereon a contact array 216. In thedepicted example, contact array 216 comprises both optical contacts 220and electrical contacts 230.

There are a variety of types of intra-cochlear stimulating assembliesincluding short, straight and perimodiolar. For example, lateral wallarray stimulating assemblies that sit, after implantation, in thecochlea away from the modiolus can be used with the technologiesdescribed herein. The depicted peri-modiolar stimulating assembly 218 isconfigured to adopt a curved configuration during and or afterimplantation into the recipient's cochlea. To achieve this, in certainarrangements, stimulating assembly 218 is pre-curved to the same generalcurvature of a cochlea. Such examples of stimulating assembly 218, aretypically held straight by, for example, a stiffening stylet (not shown)or sheath which is removed during implantation, or alternatively varyingmaterial combinations or the use of shape memory materials, so that thestimulating assembly can adopt its curved configuration when in thecochlea. Other methods of implantation, as well as other stimulatingassemblies which adopt a curved configuration, can be used and aredescribed herein.

Stimulating assembly 218 can also be a non-perimodiolar stimulatingassembly. For example, stimulating assembly 218 can include a straightstimulating assembly or a mid-scala assembly which assumes a midscalaposition during or following implantation.

Alternatively, the stimulating assembly can be a short electrodeimplanted into at least in basal region. The stimulating assembly canextend towards apical end of cochlea, referred to as cochlea apex. Incertain circumstances, the stimulating assembly can be inserted intocochlea via a cochleostomy. In other circumstances, a cochleostomy canbe formed through round window, oval window, the promontory or throughan apical turn of cochlea.

Internal component 244 further comprises a lead region 208 couplingstimulator/receiver unit 202 to stimulating assembly 218. Lead region208 comprises a region 204 which is commonly referred to as a helixregion, however, the required property is that the lead accommodatemovement and is flexible, it does not need to be formed from wire woundhelically. Lead region also comprises a transition region 206 whichconnects helix region 204 to stimulating assembly 218. As describedbelow, optical and/or electrical stimulation signals generated bystimulator/receiver unit 202 are delivered to contact array 216 via leadregion 208. Helix region 204 prevents lead region 208 and its connectionto stimulator/receiver 202 and stimulating assembly 218 from beingdamaged due to movement of internal component 244 (or part of 244) whichcan occur, for example, during mastication.

FIG. 3 is a schematic diagram of a hybrid electrically- andmechanically-stimulating cochlear implant auditory prosthesis 300. Theprosthesis 300 is a cochlear implant having implantable and externalportions, as described elsewhere herein. As such, not all components arenecessarily described. A behind-the-ear (BTE) portion 302 contains amicrophone 304 and a sound processing unit 306. An electrical signal 308representing a sound signal 310 detected by the microphone 304 isprovided from the microphone 304 to the sound processing unit 306. Thesound processing unit 306 implements one or more sound processing and/orcoding strategies to convert the pre-processed microphone output intodata signals 312. The data signals 312 are sent via a tethered cable 314to an external portion 316 of the prosthesis 300. The external portion316 is held in contact with an implantable portion 318 via a magneticretention force. A transceiver 320 in the external portion 316communicates with a corresponding transceiver 322 in the implantableportion 318. Signals 323 received by the implantable transceiver 322 arerouted to one of two stimulation units within the implantable portion318, via a signal differentiation module 325. The signal differentiationmodule 325 is configured to identify the incoming signals 323 and sendthe appropriate signals 324, 326 to the appropriate stimulation unit. Afirst, or electrical, stimulation unit 328 generates electricalstimulation signals 330 for delivery to the cochlea of the recipient,via a hybrid stimulating assembly 332. A second, or mechanical,stimulation unit 334 generates electrical stimulation signals 336 fordelivery to the cochlea of the recipient, again via the hybridstimulating assembly 332.

The electrical stimulation unit 328 and the mechanical stimulation unit334 both deliver electrical stimulation signals 330, 336 to therecipient. The signals 330, 336, however, have different characteristicsand are connected to different stimulators within the hybrid stimulatingassembly 332. The signals 330 are delivered via one or more electrodes338 within the hybrid assembly 332, as with the cochlear implantsdescribed above. A discrete electrode 338 acts as an electricalstimulator, delivering electrical stimuli directly to the cochlea. Inexamples, the signals 330 are delivered directly into the cochlea. Thesignals 336 are delivered to one or more coils 340 within the hybridassembly 332. The coils (and any associated magnets, as described below)act as a mechanical stimulator delivering mechanical stimuli directly tothe cochlea. These signals 336 are pass through the coil(s) 340 to causethe hybrid stimulating assembly 332 to expand and contract (or stretchand return). In examples, the coil(s) 340 can be manufactured of abiocompatible material such as platinum, or can be embedded in a rigidbiocompatible material such as polyether ether ketone (PEEK),polyphenylsulfone (PPSU), or other comparable rigid plastics. Asdescribed below, in certain examples, magnets are used in conjunctionwith the coils 340. Those magnets may also be embedded in abiocompatible material, such as those described above. In otherexamples, the signals can cause the hybrid assembly 332 to vibratewithin the cochlea or otherwise deform. The deformation and/or vibrationprovides mechanical stimulation to the recipient through acoustic wavesthat travel toward the apical end of the cochlea through the perilymph.Certain contemplated embodiments of hybrid electrode assemblies arefurther described below.

Cochlear implants that deliver both electrical stimulation andmechanical stimulation, such as those described herein, can be utilizedin a variety of configurations. For example, conventional cochlearimplants can have up to twenty-two electrodes for delivery of stimuli toa recipient, each delivering a signal associated with a specificreceived sound frequency range. The stimulus is typically in the form ofelectrical stimuli delivered directly to the cochlea/nerve. The coilsutilized in the hybrid systems described herein can replace one or moreof these electrodes, or can be used to supplement the output of one ormore electrodes. In examples, the mechanical stimulus produced by thecoil movement can be on a lower range of the audible human frequency,such as below 2 kHz, 1.5 kHz or 1 kHz. Low frequency mechanicalstimulation can be used in conjunction with a short electrode array thatis implanted in the basal region of the cochlea (i.e. not past the basalturn) to help preserve low frequency hearing. The electrical contacts onthe electrode array can stimulate a high frequency range not stimulatedacoustically.

Mechanical stimulation to the cochlea can be desirable for recipientswho have retained some measure of residual hearing. These recipientstypically retain such hearing at very low frequencies. The mechanicalstimulation creates a wave within the cochlea fluid that resonateswithin the cochlea at particular frequencies, for example, the residuallower frequencies. The mechanical stimulation, then, lends itself moredesirably to the use of straight stimulating arrays. Since thestimulating array expands and contracts within the cochlea (as describedin more detail below), straight assemblies that to not penetrate deepinto the cochlea may be desirable, since they can be inserted so as notto contact the basilar membrane of the cochlea. Contact between thestimulating assembly and basilar membrane can reduce the efficacy of themechanical stimulation by impeding vibration or can damage the membranestructure. Additionally, straight assemblies can be more desirable sincethey can retain the residual hearing, again because they are notinserted as deeply into the cochlea. Regardless, curved stimulatingassemblies can be utilized with the present technology in certainapplications.

Mechanical stimulation to the cochlea can have other advantages. Withelectrical stimulation provided by electrodes within a cochlear implant,there are often overlaps in frequency ranges produced by the variouselectrodes, or gaps between the frequency ranges of adjacent electrodes.Mechanical stimulation, however, can produce a finer spectrum of sound,thereby eliminating or reducing such gaps and overlaps in situationswhere the recipient retains some residual hearing. Additionally,mechanical stimulation can be better suited to delivering lowerfrequencies within the hearing spectrum. Certain embodiments of thehybrid systems, then, can utilize mechanical stimulation for receivedsounds lower than about 1 kHz. Electrical stimulation can be used todeliver signals to the cochlea for sounds in excess of 1 kHz.Additionally, the mechanical stimulators incorporated into thestimulating assemblies described herein can be positioned based on theirassociated sound frequency. That is, mechanical stimulators that areconfigured to deliver stimuli associated with lower frequency signalscan be disposed more apically within the cochlea, toward a distal end ofthe intra-cochlear region. Mechanical stimulators that are configured todeliver stimuli associated with higher frequency signals can be disposedmore basally within the cochlea, toward a proximal end of theintra-cochlear region.

FIG. 4 is a partial schematic view of an intra-cochlear region 400 of ahybrid stimulating assembly. The intra-cochlear region 400 includes anelongate carrier 402 that is depicted in a straight configuration,having an axis A, for clarity. This region 400 includes a number ofelectrodes 404 disposed on the surface thereof. Each electrode 404 isconnected to the electrical stimulation unit of FIG. 3 via a pair ofdiscrete leads or wires 404 a (only one of which is shown for clarity).The intra-cochlear region 400 also includes a coil 406 disposedproximate a tip 408 thereof. Leads or wires 410 a, 410 b connect thecoil 406 to the mechanical stimulation unit of FIG. 3. A piece ofmagnetic material 412 is disposed proximate the coil 406. Morespecifically, the magnetic material 412 can be disposed between the coil406 and the terminus 413 of the region 400. The magnetic material 412and coil 406 that form the mechanical stimulator are disposed betweenthe most distal electrode 404 and the terminus 413. The magneticmaterial 412 can be a rare earth or other magnet. In examples, aneodymium magnet can be utilized. When an electrical signal is sent viathe wires 410 a, 410 b, the flux generated at the coil 406 moves themagnet 412 back and forth within the carrier 402. As such, the coil 406and magnetic material 412 function as a magnetic induction assembly and,upon receipt of the electrical signal at the coil 406, deform thecarrier 402. In examples, where the loops of the coil 406 are disposedgenerally about the axis A, the movement of the magnet 412 issubstantially axially along axis A. Since the carrier 402 is a generallyflexible material, such as silicone, movement of the magnet 412 causesan axial stretching and deformation of the carrier 402. The maximumdeformation may be a distance d, and can be proportional to thefrequency of the signal sent along wires 410 a, 410 b. In examples, thetotal deformation can be up to about 10 microns. In certain examples,relative higher frequencies will stretch the carrier 402 less thanrelatively lower frequencies. The total stretch, and therefore totalstimulation provided therefrom, can be dependent on a number of factors.Such factors include, but are not limited to, the resistance of thewires, electrical signal being delivered, the durometer of the siliconecarrier, the number of turns on the coils, the magnetic strength of themagnet, and so on.

FIG. 5 is a partial schematic view of an intra-cochlear region 500 of ahybrid stimulating assembly. The intra-cochlear region 500 includes anelongate carrier 502 that is depicted in a straight configuration,having an axis A. This region 500 includes a number of electrodes 504disposed on the surface thereof. Each electrode 504 is connected to theelectrical stimulation unit of FIG. 3 via a pair of discrete leads orwires 504 a (only one of which is shown for clarity).

This example includes two coils 506, 514, proximate a tip 508 thereof.Leads or wires 510 a, 510 b connect the coil 506 to the mechanicalstimulation unit of FIG. 3, as above. A second coil 514 is connected tothe mechanical stimulation unit of FIG. 3 with leads or wires 516 a, 516b. Moreover, the first coil 506 and second coil 514 that form themechanical stimulator are disposed between the most distal electrode 504and a terminus 513 of the region 500. Unlike the example of FIG. 4,however, this intra-cochlear region 500 does not utilize any magneticmaterial. As such, it can be safer for a recipient that is subjected tomagnetic resonance imaging (MRI) procedures. When an electrical signalis sent via the associated wires to the coils 506, 514, the fluxgenerated between the two coils 506, 514 moves coils 506, 514 within thecarrier 502. In an example, the electrical signal delivered to coil 506is an electrical current that is out of phase with the electricalcurrent delivered to coil 514. As such, the coils 506, 514 function as amagnetic induction assembly and, upon receipt of these out of phaseelectrical signals of the coils 506, 514, deform the carrier 502. Wherethe loops of the coils 506, 514 are disposed generally about the axis A,the movement of the coils 506, 514 is substantially axially along axisA. This movement causes an axial stretching or deformation of thecarrier 502. The maximum deformation may be a distance d, and can beproportional to the frequency of the signal sent to the coils 506, 514.

FIG. 6 is a partial schematic view of an intra-cochlear region 600 of ahybrid stimulating assembly. The intra-cochlear region 600 includes anelongate carrier 602 that is depicted in a straight configuration,having an axis A, for clarity. This region 600 includes a number ofelectrodes 604 disposed on the surface thereof. Each electrode 604 isconnected to the electrical stimulation unit of FIG. 3 via a pair ofdiscrete leads or wires 604 a (only one of which is shown for clarity).The intra-cochlear region 600 also includes a coil 606 disposedproximate a tip 608 thereof. Leads or wires 610 a, 610 b connect thecoil 606 to the mechanical stimulation unit of FIG. 3. A piece ofmagnetic material 612 is disposed proximate the coil 606 and formstherewith a magnetic induction assembly. Moreover, the magnetic material612 and the first coil 606 that form the mechanical stimulator aredisposed between the most distal electrode 604 and a terminus 613 of theregion 600. When an electrical signal is sent via the wires 610 a, 610b, the flux generated at the coil 606 moves the magnet 612 back andforth within the carrier 602. In examples, where the loops of the coil606 are disposed generally about an axis T that is transverse to theaxis A, the movement of the magnet 612 is substantially transverse toaxis A. Since the carrier 602 is a generally flexible material, such assilicone, movement of the magnet 612 causes a transverse stretching ordeformation of the carrier 602. The maximum deformation may be adistance d, and can be proportional to the frequency of the signal sentalong wires 610 a, 610 b. In certain examples, relative higherfrequencies will stretch the carrier 602 less than relatively lowerfrequencies.

FIG. 7 is a partial schematic view of an intra-cochlear region 700 of ahybrid stimulating assembly. The intra-cochlear region 700 includes anelongate carrier 702 that is depicted in a straight configuration,having an axis A. This region 700 includes a number of electrodes 704disposed on the surface thereof. Each electrode 704 is connected to theelectrical stimulation unit of FIG. 3 via a pair of discrete leads orwires 704 a (only one of which is shown for clarity).

Like the example of FIG. 5, this example includes two coils 706, 714,proximate a tip 708 thereof. Leads or wires 710 a, 710 b connect thecoil 706 to the mechanical stimulation unit of FIG. 3, as above. Asecond coil 714 is connected to the mechanical stimulation unit of FIG.3 with leads or wires 716 a, 716 b. Moreover, the first coil 706 andsecond coil 714 that form the mechanical stimulator (as well as amagnetic induction assembly) are disposed between the most distalelectrode 704 and a terminus 713 of the region 700. When an electricalsignal (e.g., out of phase currents, as described above) is sent via theassociated wires to the coils 706, 714, the flux generated between thetwo coils 706, 714 moves coils 706, 714 within the carrier 702. Unlikethe example of FIG. 5, however, the coils 706, 714 are disposedgenerally on opposite sides of the axis A, aligned with an axis T thatis transverse to axis A, aligned with an axis T that is transverse toaxis A. As such, the movement of the coils 706, 714 is substantiallytransverse or orthogonal to the axis A. This movement causes atransverse stretching or deformation of the carrier 712, which can bedefined by a distance d, and can be proportional to the frequency of thesignal sent to the coils 706, 714.

The coil configurations of FIGS. 4-7 result in deformation in differentdirections, based on the configuration of the coil(s) and/or magneticmaterial. These figures depict the carrier stretching only axially ororthogonally (transversely). It will be apparent, however, thatstretching can be in generally any direction (relative to the axis A),depending on the location of the coil(s) and magnet (if used). Forexample, each of a coil and a magnet can define an angle to the axis Aof less than about 90°. Angles of about 45° to about 85° and about 60°to about 75° are contemplated. Other angles can be utilized.

FIG. 8 depicts a method 800 of providing stimuli with a hybrid electrodeassembly, e.g., for a cochlear implant. The method 800 includesdelivering a first stimulus from a first stimulation unit, operation802. This stimulation element can be disposed within an implantedportion of an auditory prosthesis such as a cochlear implant. Inoperation 804, a second stimulus is delivered from a second stimulationunit. The second stimulus displays a different characteristic than thefirst stimulus. For example, as described herein, the first stimulus canbe a first signal, while the second stimulus can be a second signaldifferent from the first signal. The electrical signal causes a housingof the cochlear implant (more specifically, the stimulating assembly) todeform (e.g., expand and contract or stretch and return), thusdelivering a mechanical stimulus to the cochlea of the recipient.Depending on the orientation of the mechanical stimulator within thestimulating assembly, the stretching may be axially along thestimulation assembly, or may be at an angle thereto.

This disclosure described some aspects of the present technology withreference to the accompanying drawings, in which only some of thepossible aspects were shown. Other aspects can, however, be embodied inmany different forms and should not be construed as limited to theaspects set forth herein. Rather, these aspects were provided so thatthis disclosure was thorough and complete and fully conveyed the scopeof the possible aspects to those skilled in the art.

Although specific aspects were described herein, the scope of thetechnology is not limited to those specific aspects. One skilled in theart will recognize other aspects or improvements that are within thescope of the present technology. Therefore, the specific structure,acts, or media are disclosed only as illustrative aspects. The scope ofthe technology is defined by the following claims and any equivalentstherein.

1-20. (canceled)
 21. An apparatus comprising: an elongate carrier havingan intra-cochlear region; an electrical stimulator disposed at theintra-cochlear region of the elongate carrier and being configured todeliver an electrical stimulus to a cochlea of a recipient; and amechanical stimulator disposed in the intra-cochlear region of theelongate carrier and being configured to deliver mechanical stimulationto the cochlea of the recipient, wherein the mechanical stimulator isdisposed at the intra-cochlear region such that the mechanicalstimulator is located at a basal region of a recipient's cochlea whenthe elongate carrier is implanted.
 22. The apparatus of claim 21,wherein the mechanical stimulator includes two induction coilsencapsulated in the elongate carrier.
 23. The apparatus of claim 22,wherein the mechanical stimulator further includes a magnet encapsulatedin the elongate carrier.
 24. The apparatus of claim 22, wherein the twoinduction coils are aligned along an axis of the elongate carrier. 25.The apparatus of claim 21, wherein the mechanical stimulator includes acoil and a permanent magnet encapsulated in the elongate carrier. 26.The apparatus of claim 21, wherein the elongate carrier includes adistal end that terminates at a tip of the elongate carrier; wherein theelectrical stimulator is disposed at a location between the tip and themechanical stimulator.
 27. The apparatus of claim 21, wherein theelectrical stimulator comprises a plurality of electrical contacts. 28.The apparatus of claim 21, wherein an electrical signal directed to themechanical stimulator causes an expansion of the elongate carrier. 29.The apparatus of claim 21, wherein the mechanical stimulator isconfigured to deliver stimuli associated with lower frequency signalsthan the electrical stimulator.
 30. An apparatus comprising: an elongatecarrier having an intra-cochlear region, wherein the intra-cochlearregion comprises a proximal intra-cochlear region and a distalintra-cochlear region; a mechanical stimulator disposed within theproximal intra-cochlear region; and a plurality of electrodes exposed ona surface of the intra-cochlear region.
 31. The apparatus of claim 30,wherein the mechanical stimulator comprises a first coil and a secondcoil; wherein the elongate carrier comprises a flexible body thatdefines an elongate axis; and wherein the first coil is substantiallyaxially aligned with the second coil along the elongate axis.
 32. Theapparatus of claim 30, wherein the mechanical stimulator comprises afirst coil and a second coil; wherein the elongate carrier comprises aflexible body that defines an elongate axis, and wherein each of thefirst coil and the second coil are embedded within the flexible bodyalong a coil axis substantially transverse to the elongate axis.
 33. Theapparatus of claim 30, wherein the mechanical stimulator comprises afirst coil and a second coil; wherein the elongate carrier comprises aflexible body that includes an elongate axis; wherein each of the firstcoil and the second coil is configured to receive an electrical currentthat is out of phase with the electrical current in the other coil; andwherein receipt of the respective currents causes the elongate carrierto stretch along the elongate axis.
 34. The apparatus of claim 30,wherein the mechanical stimulator comprises a first coil and a magnetdisposed within the elongate carrier proximate the first coil.
 35. Amethod comprising: delivering a first stimulus as acoustic wavesgenerated from an intra-cochlear region of a cochlear implant toward anapical end of a recipient's cochlea; and delivering a second stimulusvia the cochlear implant that is different than the first stimulus. 36.The method of claim 35, wherein the second stimulus is an electricalstimulus.
 37. The method of claim 35, wherein the intra-cochlear regionof the cochlear implant does not extend past a basal turn of therecipient's cochlea.
 38. The method of claim 35, wherein the firststimulus delivers signals corresponding to sounds less than 2 kHz. 39.The method of claim 38, wherein the first stimulus delivers signalscorresponding to sounds less than 1.5 kHz.
 40. The method of claim 39,wherein the first stimulus delivers signals corresponding to sounds lessthan 1 kHz.